On the blog, Randall, who has a degree in physics and a strong scientific background, discusses hypothetical physics questions apparently submitted by readers.
Since 2014, there's also a book of the blog.

Unlike other sites which answer readers' questions, what if? typically takes the question beyond the original scope likely intended by the reader and takes it to some extreme for humorous effect. For example, in the first article, he discusses what would happen if a baseball were pitched at 90% of the speed of light. After effectively describing what would occur as a nuclear explosion, leveling the stadium and the surrounding mile radius, he concludes with the note "A careful reading of official Major League Baseball Rule 6.08(b) suggests that in this situation, the batter would be considered 'hit by pitch', and would be eligible to advance to first base."

The questions Randall tackles range from realistic possibilities (e.g. the probability of achieving a perfect SAT score by guessing) to completely fictional questions (e.g. How much Force power can Yoda output?). In his explanations, Randall, often uses diagrams in an xkcd style. Regardless of the context, Randall tends to take the questions extremely literally and responds seriously to them, even if they are whimsical (such as the Yoda question). This is clear from his response to the question of what would happen if everybody on Earth stood together and jumped at the same time. After acknowledging that the question has been answered elsewhere, he recaps the result, but then focuses more intently on the unasked resulting issue of the aftermath of everyone on Earth being magically transported to one location as they all try to return home.

Contents

Randall announced his what if? book on 12 March 2014 in the blag. It was published on September 2, 2014, and the UK edition of the book was published on September 4, 2014. It is the 2nd book published by Randall.

The general cover of the book

The alternate cover of the book

It is just like 'xkcd:volume 0' a compilation of some questions from the website, but half of them are new.

In the UK edition of the book, Randall included a preface about his thoughts on the units used in the UK. (The Metric System)

Randall Munroe left NASA in 2005 to start up his hugely popular site XKCD 'a web comic of romance, sarcasm, math and language' which offers a witty take on the world of science and geeks. It now has 600,000 to a million page hits daily. Every now and then, Munroe would get emails asking him to arbitrate a science debate. 'My friend and I were arguing about what would happen if a bullet got struck by lightning, and we agreed that you should resolve it . . . ' He liked these questions so much that he started up What If.

If your cells suddenly lost the power to divide, how long would you survive?

How dangerous is it, really, to be in a swimming pool in a thunderstorm?

If we hooked turbines to people exercising in gyms, how much power could we produce?

What if everyone only had one soulmate?

When (if ever) did the sun go down on the British empire?

How fast can you hit a speed bump while driving and live?

What would happen if the moon went away?

In pursuit of answers, Munroe runs computer simulations, pores over stacks of declassified military research memos, solves differential equations, and consults with nuclear reactor operators. His responses are masterpieces of clarity and hilarity, studded with memorable cartoons and infographics. They often predict the complete annihilation of humankind, or at least a really big explosion. Far more than a book for geeks, WHAT IF: Serious Scientific Answers to Absurd Hypothetical Questions explains the laws of science in operation in a way that every intelligent reader will enjoy and feel much the smarter for having read.

The summary on the back of the UK edition of the book reads:

Hey! Thanks for looking at my book. If you're thinking about buying it, here are some things you might want to know:

Humans can't digest the cellulose in paper, but if we could, eating this book would give you about 2,300 calories (including the cover).

This book can't stop most bullets; if you want to use it for armour, you may want a lot more than one copy.

If you have a good arm, you could probably throw this book about 45 feet. With practice, it's possible to throw a book every 800 milliseconds, which means that if human attackers are sprinting towards you, you'll have three or four chances to hit them before they reach you. If, on the other hand, you're being attacked by a coyote, it's higher top speed means you'll have only one chance to hit it. Aim carefully.

HIDDEN FEATURE: The inside of this book has words and pictures, plus a special UK foreword. It answers many important questions, including whether you could jump from a plane with a helium tank and inflate balloons fast enough to slow your fall and survive (yes) and whether you could hide from a supersonic windstorm in Finland (yes, but it won't help).

The two first articles were released on the same day, Tuesday July 10, 2012, probably to get the blog going, and let users of xkcd see that there was going to be more.

After that they were released weekly for almost three years, with just a few times with two (and once three) weeks between releases, up until article 136 was released on April 12, 2015 (2 years and 40 weeks).

First after 25 releases was there a two week Christmas break before article 26 was released on December 31, 2012.

After that there were five more two weeks break, one three week break (before December 11, 2014) and two releases in a row (133-134 towards the end of this period of 136 articles), where the release dates where shifted so the two came out over three weeks' time with about 1.5 weeks between them.

The second break came a year after the first and was also a Christmas break before article 77 was released on December 31, 2013

Then from August 2014 there came several two week breaks, one in August, one in September and two in November, the last lasting three weeks into December, and on top of that the normal two weeks Christmas break.

After this less orderly period there came a period of 10 weeks in a row with 10 releases starting on January 1, 2015.

The release day was fixed to once a week on a given weekday, except for a few articles that were delayed a day (or two) in one week, but then next week's article would again be released on the normal day.

To begin with the release day was Tuesdays, and the third article was released a week after the first two on Tuesday July 17, 2012.

The release day shifted to Wednesday from article 100 released on Wednesday June 11, 2014.

The release day shifted once more to Thursday from article 117 released on Thursday October 23, 2014.

The final six articles in this period were released on four different week days, only two of them with one week apart.

The result of the above is that over the first 144 weeks 136 articles where released with never more than 3 weeks between releases. As the first two were released on week 1, this means that there were 134 articles released over the next 143 weeks, meaning there were only 9 weeks without an article.

After article 136 was released on April 12, 2015, Randal took a 13 week break from updates until July 14, 2015.

At the time Randall wrote a note stating "What If updates are temporarily on hold, and will resume on July 14th, 2015 at 7:49:59 AM EDT."

This was the date and time that the New Horizons probe achieved its closest approach to Pluto.

The article 137 from July 14, 2015 was about the New Horizons probe.

After the break only three articles were released, two more were released after article 137 over three weeks, the last article 139 released on August 4, 2015.

But then there were two more breaks, so only one more article was released in 2015, with article 150 released after more than 6 weeks on September 18, 2015.

First after 17 more weeks releases began again with article 141 on Tuesday January 16, 2016.

After that articles began coming out regularly with a total of 9 releases out before the end of March 2016, mainly on Tuesdays to begin with, then one on a Friday before the last two came on Saturdays with two weeks breaks before each, the last being article 149 on March 26, 2016.

Since then only three more articles were released in 2016, the first two with about 8 weeks between them and then more than 12 weeks.

So during the summer of 2016, it seemed it was down to about one release every two months but then it increased.

The what if? has not stopped but the first comic in 2017 (#153, January 30, 2017) came almost 15 weeks after the last in 2016, more than three months between releases. This was so far the second longest break.

But the next one (#154) was indeed released only a bit more than week after the one with 15 weeks break, and then less than 3 weeks after followed yet an article on February 28 2017.

It was almost a year ago that two comics had been released with less than two full weeks between them (that was #147 released February 26, 2016). In the year following that release only 8 articles where released including both #147 and #154.

Interesting to see if they will begin appearing regularly again during the spring of 2017, as seems possible with three articles in less than a month and #156 was again released with less than two weeks between it and #155.

It then seemed to stop completely after those two, and it took more than a year (62 weeks) before #157 came out in May 2018.

See more details for breaks in the releases in the table with a list of all the articles down below.

At the moment it seems impossible to guess when a new post is released so:

It would be nice if anyone noticing a new post, that they made a note in the discussion of the next comic released.

How long would the Sun last if a giant water hose were focused upon it? My sixth grade brother, Adam, asked me this.

What if you shined a flashlight (or a laser) into a sphere made of one-way mirror glass?

If Michael Phelps could hold his breath indefinitely, how long would it take for him to reach the lowest point in the ocean and back if he swam straight down and then straight back up?

In the first Superman movie, Superman flies around Earth so fast that it begins turning in the opposite direction. This somehow turns back time [... ] How much energy would someone flying around the Earth have to exert in order to reverse the Earth's rotation?

How fast would you have to go in your car to run a red light claiming that it appeared green to you due to the Doppler Effect?

What would happen if you opened a portal between Boston (sea level) and Mexico City (elev. 8000+ feet)?

When my wife and I started dating she invited me over for dinner at one time. Her kitchen had something called Bauhaus chairs, which are full of holes, approx 5-6 millimeters in diameter in both back and seat. During this lovely dinner I was forced to liberate a small portion of wind and was relieved that I managed to do so very discretely. Only to find that the chair I sat on converted the successful silence into a perfect, and loud, flute note. We were both (luckily) amazed and surprised and I have often wondered what the odds are for something like that happening. We kept the chairs for five years but despite laborious attempts it couldn't be reproduced.

In Armageddon, a NASA guy comments that a plan to shoot a laser at the asteroid is like “shooting a b.b. gun at a freight train.” What would it take to stop an out-of-control freight train using only b.b. guns?

40000 people and some magic. Stopping an asteroid with a laser on the other hand is a lot easier.

I've been told that if the Earth were shrunk down to the size of a bowling ball, it would be smoother than said bowling ball. My question is, what would a bowling ball look like if it were blown up to the size of the Earth?

What if one were to drop 3,000 bouncy balls from a seven story parking structure onto a person walking on the sidewalk below? Should the person survive, what would be the number of bouncy balls needed to kill them? What injuries would occur and what would the associated crimes be?

How quickly would the ocean's drain if a circular portal 10 meters in radius leading into space was created at the bottom of Challenger Deep, the deepest spot in the ocean? How would the Earth change as the water is being drained?

What if a huge mountain—Denali, say—had the bottom inch of its base disappear? What would happen from the impact of the mountain falling 1 inch? What about 1 foot? What if the mountain's base were raised to the present height of the summit, and then the whole thing were allowed to drop to the earth?

What if a spacecraft slowed down on re-entry to just a few miles per hour using rocket boosters like the Mars-sky-crane? Would it negate the need for a heat shield?

Is it possible for a spacecraft to control its reentry in such a way that it avoids the atmospheric compression and thus would not require the expensive (and relatively fragile) heat shield on the outside?

Could a (small) rocket (with payload) be lifted to a high point in the atmosphere where it would only need a small rocket to get to escape velocity?

What if I jumped out of an airplane with a couple of tanks of helium and one huge, un-inflated balloon? Then, while falling, I release the helium and fill the balloon. How long of a fall would I need in order for the balloon to slow me enough that I could land safely?

I was absentmindedly stirring a cup of hot tea, when I got to thinking, "aren't I actually adding kinetic energy into this cup?" I know that stirring does help to cool down the tea, but what if I were to stir it faster? Would I be able to boil a cup of water by stirring?

I use one of those old phones where you type with numbers—for example, to type "Y", you press 9 three times. Some words have consecutive letters on the same number. When they do, you have to pause between letters, making those words annoying to type. What English word has the most consecutive letters on the same key?

Is there any way to fire a gun so that the bullet flies through the air and can then be safely caught by hand? e.g. shooter is at sea level and catcher is up a mountain at the extreme range of the gun.

Astrophysicists are always saying things like "This mission to this comet is equivalent to throwing a baseball from New York and hitting a particular window in San Francisco." Are they really equivalent?

Assuming that you have a spaceship in orbit around the Earth, could you propel your ship to speeds exceeding escape velocity by hitting golf balls in the other direction? If so, how many golf balls would be required to reach the Moon?

In terms of human-made objects, has Voyager 1 travelled the farthest distance? It's certainly the farthest from Earth we know about. But what about the edge of ultracentrifuges, or generator turbines that have been running for years, for example?

I've occasionally seen "radar enforced" on speed limit signs, and I can't help but ask: How intense would radio waves have to be to stop a car from going over the speed limit, and what would happen if this were attempted?

Intense enough to cause a medium sized nuclear explosion. Better to just carry a sign.

If all the seas were one sea, What a great sea that would be! If all the trees were one tree, What a great tree that would be! If all the men were one man, What a great man that would be! If all the axes were one axe, What a great axe that would be! And if the great man took the great axe, And cut down the great tree, And let if fall into the great sea, What a great splish-splash that would be!
... How great would all of these things be?

My daughter — age 4.5 — maintains she wants a billion-story building. It turns out not only is that hard to help her appreciate this size, I am not at all able to explain all of the other difficulties you'd have to overcome.

First of all, it would bot stand under it's own weight. Also, it would be many times the distance the Earth is from the Moon.

What took more energy, the building of the Great Pyramid of Giza or the Apollo Mission? If we could convert the energy to build the Great Pyramid, would it be enough to send a rocket to the Moon and back?

Suppose you were to print, in 12 point text, the numeral 1 using a common cheap ink-jet printer. How many molecules of the ink would be used? At what numerical value would the number printed approximately equal the number of ink molecules used?

People sometimes say "If I had all the money in the world ..." in order to discuss what they would do if they had no financial constraints. I'm curious, though, what would happen if one person had all of the world's money?

My 12-year-old daughter is proposing an interesting project. She is planning to attach a number of helium balloons to a chair, which in turn would be tethered by means of a rope to a Ferrari. Her 13-year-old friend would then drive the Ferrari around, while she sits in the chair enjoying uninterrupted views of the countryside. Leaving aside the legal and insurance difficulties, my daughter is keen to know the maximum speed that she could expect to attain, and how many helium balloons would be required.

When I was about 8 years old, shoveling snow on a freezing day in Colorado, I wished that I could be instantly transported to the surface of the Sun, just for a nanosecond, then instantly transported back. I figured this would be long enough to warm me up but not long enough to harm me. What would actually happen?

you would not be warmed if you went to the surface. The core on the other hand, would vapourize you.

If you stripped away all the rules of car racing and had a contest which was simply to get a human being around a track 200 times as fast as possible, what strategy would win? Let's say the racer has to survive.

Stopping rain from falling on something with an umbrella or a tent is boring. What if you tried to stop rain with a laser that targeted and vaporized each incoming droplet before it could come within ten feet of the ground?

If you made an elevator that would go to space (like the one you mentioned in the billion-story building) and built a staircase up (assuming regulated air pressure) about how long would it take to climb to the top?

What in my pocket actually contains more energy, my Zippo or my smartphone? What would be the best way of getting the energy from one to the other? And since I am already feeling like Bilbo in this one, is there anything else in my pocket that would have unexpected amounts of stored energy?

I've long thought about putting a flamethrower on the front of a car to melt snow and ice before you drive across it. Now I've realized that a flamethrower is impractical, but what about a high-powered microwave emitter?

I have had a particular problem for as long as I can remember. Any time I attempt to heat left over Chinese food in a microwave, it fails to heat completely through somewhere. Usually the center but not always and usually rice, but often it will be a small section of meat. It's baffling and has made me automatically adjust heating times to over 2 minutes. In most cases this tends to heat the bowl or plate more than the food. So I suppose the question is what is the optimal time to heat left over Chinese food in the microwave, how about an 800 watt microwave?

The release date in the archive is the wrong year 2014. From here on there seems to no longer be a standard release day for some time.

I saw a sign at a hot springs tub saying "Caution: Water is hotter than average" with water at about 39°C. Although they were presumably trying to say "hotter than the average swimming pool," this got me wondering: What is the average temperature of all water on the Earth’s surface, and how does that temperature compare to 39°C?

So, you're falling from a height above the tallest building in your town, and you don't have a parachute. But wait! Partway down the side of that skyscraper there's a flagpole sticking out, sans flag! You angle your descent and grab the pole just long enough to swing around so that when you let go you're now heading back up toward the sky. As gravity slows you and brings you to a halt, you reach the top of the skyscraper, where you reach out and pull yourself to safety. What's the likelihood this could happen?

The first of two longer shifts in release day two weeks in a row which resulted in only two releases over three weeks, resulting in the eight break in total.

I've often joked I'd like to have my remains put into orbit. Not in a "scatter my ashes" sense, but, like, "throw my naked corpse out the airlock" sense. Honestly, my main motivation is to baffle someone in the distant future, but it's an interesting scientific question: what would happen to my body in orbit over the course of years, decades or centuries?

The second of two longer shifts in release day two weeks in a row which resulted in only two releases over three weeks, resulting in the eight break in total.

Which has a greater gravitational pull on me: the Sun, or spiders? Granted, the Sun is much bigger, but it is also much further away, and as I learned in high school physics, the gravitational force is proportional to the square of the distance.

I understand that the New Horizons craft used gravity assist from Jupiter to increase its speed on the way to Pluto. I also understand that by doing this, Jupiter slowed down very slightly. How many flyby runs would it take to stop Jupiter completely?

What would happen if one tried to funnel Niagara Falls through a straw?

From here on there is no longer any standard release days. Answer: The International Niagara Committee, the International Niagara Board of Control, the International Joint Commission, the International Niagara Board Working Committee, and probably the Great Lakes–St. Lawrence River Adaptive Management Committee would be angry. Also, the Earth would be destroyed.

My boyfriend recently took a flight on a plane with wifi, and while he was up there, wistfully asked if I could send him a pizza. I jokingly sent him a photo of a parrot holding a pizza slice in its beak. Obviously, my boyfriend had to go without pizza until he landed at JFK. But this raised the question: could a bird deliver a standard 20" New York-style cheese pizza in a box? And if so, what kind of bird would it take?

Second two months break of at least two in a row, the 16th break in total. The release date in the archive is the wrong month June. It was released between 18-20 July, as the link here was posted on the 20th. But on the archive page is says it was released on June 21, which should probably have been July 21.

Since Death Valley is below sea level could we dig a hole to the ocean and fill it up with water?

After two 8 weeks breaks this one waited almost three months. Regarding the question it could be done, but why did the guy asking the question whish to do such a horrible thing Randall ends up asking back. Most of the what if? goes with citing temperature records and other trivia actually naming a Jeopardy master. At least two comics coming out right after this was referencing this article. 1748: Future Archaeology and 1750: Life Goals.

Earth’s atmosphere is really thin compared to the radius of the Earth. How big a hole do I need to dig before people suffocate?

With close to 15 weeks this was the second longest break between articles so far. The hole needs to be Very big it turns out, but under the right circumstances a five mile hole over the entire state of Texas might suffice... But beware of messing with the Texans.

What if the entire continental US was on a decreasing slope from West to East. How steep would the slope have to be to sustain the momentum needed to ride a bicycle the entire distance without pedaling?

The article is about the slope needed to be able to coast on a bike, without using the pedals, across mainland USA. It turns out the ramp would need to be five miles high (8 km) to make this possible, and that would be at a speed slower than walking. Also you would need oxygen the first third of the way down... Unlike the last article, out after almost a 15 weeks break, this one was released only a bit more than week after that. It is almost a year ago that two comics have been released with less than two full weeks between them (that was #147 released February 26, 2016). In that year (assuming no more comics before February 26 2017), only 8 articles where released including both 147 and this one. Interesting to see it they will begin appearing regularly again during the spring of 2017.

With less than 3 weeks between releases, releases seems to have become more regular in the beginning of 2017. The question is not asked of Randall this time, but rather one he has found discussed on Episode 343 of the advice podcastMy Brother, My Brother and Me (links are those given in the article) where the three brothers McElroy are discussing a Yahoo! Answers question. They did not answer the question but Randall does and it is quite easy so he puts it a the top: The Toaster wins! Since it heats with 1000+ watts of heat production where a freezer only cools with 100-150 watts. Although the freezer may be up to three times as effective, it is no match for the toaster, which also heats the bread locally inside it self. A nice way to explain this, is that to a toaster any human environment feels cool, so a freezer at 258 K (-15 °C) compared to room temperature of typically 293 K (20 °C), seems like a small difference compared to the temperature of the toasters heating element of about 900 K (over 600 °C). So it makes no real difference to the toaster where it is. But please don't try this at home, and also not outside in Winnipeg, Canada to avoid getting eaten by wolves.

If the question is "would a toaster still toast bread in a freezer?" the answer requires no maths at all; since toasters work by radiating heat (effecting a chemical change and increased temperature), and freezers work by convecting heat away (reducing the temperature), then no matter how powerful the freezer and how wussy the toaster, the chemical change would still occur (though your toast might be very cold).

I used to work on a fisheries crew where we would use an electro-fisher backpack to momentarily stun small fish (30 - 100 mm length) so we could scoop them up with nets to identify and measure them. The larger fish tended to be stunned for slightly longer because of their larger surface area but I don't imagine this relationship would be maintained for very large animals. Could you electrofish for a blue whale? At what voltage would you have have to set the e-fisher?

Second time with less than two weeks between release in 2017. The answer focuses more on the bad side effects of electrofising, both long term effect on fish and also mentions killing of Dolphins. So it seems more of an protect the animal article than an answer. But the fact is that larger animals (and especially mammals) is likely to die rather than just get stunned. But it is also harder to get any effect in saltwater, which explains why electrofishing is mainly done in rivers and lakes. The higher conductivity of saltwater makes to current prefer to avoid the less salt whale rather than go through it. This is less of an issue in fresh water. So basically it just won't work on blue whales.

My son (5y) asked me today: If there were a kind of a fireman's pole from the Moon down to the Earth, how long would it take to slide all the way from the Moon to the Earth?

After two in as short period of time in March 2017 more than a year (62 weeks) passed before the next entry came in May 2018...

After a discussion of the extreme challenges that this set-up would face (an extreme form of the challenges of a space elevator), Randall details the different domains of the new slowest extreme sport: climbing out of the Moon's gravity, accelerating through the middle transfer phase, and then decelerating to your supersonic arrival on earth. Fun.